Study characteristics
The year of publication of the included trials ranged between 1998 and 2020, spanning 22 years. Twelve trials included only nulliparous women, 2 trials included only multiparous women, 4 trial included both nulliparous and multiparous women, one trials didn’t report the parity. Participants were full-term pregnant women (gestational age≥37 weeks). Four Lubricants classes were evaluated, including obstetric gel (n=8), liquid wax (n=9), liquid petroleum jelly (n=1), and peanut oil (n=1). The number of participants ranged from 62 to 800 (Table S1).